As a drug delivery system for drugs, loading the drugs on carriers, and guiding the drugs to target organs, tissues, or affected areas based on physicochemical or physiological properties of the carriers, is known. Various types of antibodies, microspheres, or magnetic bodies have been studied as carriers.
Out of these, a method for concentrating drugs along with magnetic carriers in affected areas by magnetic fields has been introduced. This method is considered especially effective for highly cytotoxic anti-tumor agents toward normal cells because the delivery method is convenient and the affected areas can be treated directly. (See, for example, Patent Document 1).
Also, the assignees of the present application use compounds that have inherent ferromagnetism without employing magnetic carriers, and propose a system that guides drugs to the target tissue by magnetic fields from outside the body. (See, for example, Patent Document 2).
A magnetism-generating means with high magnetic flux density is desired to guide a drug in the body using magnetic fields from outside the body. For example, a technique of concentrating the magnetic flux density at the peak (magnetic pole) of a magnet is introduced.
In this technique, that the magnetic flux density increased by 20% compared to when the peak is left flat, by forming the shape of the peak of the magnet so that it is a pyramid shape is introduced. (See, for example, Non-Patent Document 1).